The establishment of in vivo and in vitro models for myoclonus dystonia

Abstract

Myoclonus dystonia (DYT11, OMIM 159900) (MD) is a movement disorder characterized by bilateral alcohol responsive myoclonic jerks often seen in combination with dystonia. MD is inherited as an autosomal dominant trait with reduced penetrance upon maternal transmission. Patients with this disorder are not diminished in their intellectual capacity and have a normal life span. In 2001, mutations in the epsilon-sarcoglycan gene on human chromosome 7q21 were implicated in causing this disorder. Our laboratory identified a 2nd locus on chromosome 18p11 that co-segregates with this disorder, however, a disease causing mutation has not been identified. To establish the function of epsilon-sarcoglycan within the mammalian brain, I generated a conditional knock-out (CKO) mouse of Sgce and utilized bacterial recombineering to generate a cassette that contained a "floxed" exon 1 of epsilon-sarcoglycan. ES cells that had correctly incorporated the CKO targeting cassette were selected and used to generate 3 chimeric male mice by blastocyst injection or morula aggregation. Once germline transmission of the CKO allele has been established, these mice will be bred to Cre expressing mice to generate an sgcenull, and recapitulate the phenotype of MD patients. In addition, I also developed an in vitro model of MD using RNAi directed against epsilon-sarcoglycan in the mouse neuroblastoma cell line, N1E-115. Silencing of epsilon-sarcoglycan in this cell line resulted in a decrease in the neuronal nitric oxide synthase (nNos) and an increase in cell proliferation. This data will provide insight and direction during the characterization of the sgcenull mice.